More specifically, the objective of the present invention is to meet the need for collecting and/or concentrating biological or chemical targets and to thus be of use in the context of the detection of undesirable elements such as pathogenic microorganisms or chemical pollutants in samples such as river water, fluids of cooling towers, of domestic and drinking water supply networks, etc. The biological or chemical targets can be present in a very small amount in the samples and the detection thereof is then possible only by taking large volumes (greater than 50 ml).
The term “biological or chemical target” is intended to mean microorganisms, i.e. enveloped or nonenveloped viruses, gram-positive and gram-negative vegetative bacteria, bacteria in sporulated form, protozoa, microscopic fungi and yeasts, microplankton, pollen, animal cells and plant cells; it is also intended to mean chemical molecules (fertilizers, medicaments, pollutant chemical molecules such as byproducts of the chemical industry, phytosanitary products, etc.) or biochemical molecules (antigen, protein, hormones or endocrine system-disrupting compound, etc.).
It is known practice to use functionalized magnetic beads, i.e. magnetic beads bearing, at their surface, molecules capable of binding to desired targets, as a capture system intended for isolating and/or detecting biological or chemical targets, and various methods for capturing targets with magnetic beads have already been described; indeed, the advantage of using functionalized magnetic beads is that they have a large capture surface area, and that they can be easily recovered using a magnet and, optionally, reused after elution of the captured targets.
In particular, patent application US 2003/015028 describes a not very specific method for capturing microorganisms using a solid support to which a nutrient, in particular a carbohydrate, of said micro-organisms is bound; the solid support is preferably magnetic beads. The functioning of this method lies in the choice of the nutrient for capturing microorganisms.
patent application US 2006/0141450 describes a method for capturing cells, organelles or viruses present in samples of physiological origin using the not very specific properties of paramagnetic adsorption of magnetic beads.
The above methods are aimed at treating samples having a volume of approximately 1 ml; they are not suitable for the treatment of samples with a volume of greater than 50 ml.
International application WO 2008/131554 describes a device suitable for detecting pathogenic microorganisms using food samples; this device comprises a 500 ml Erlenmeyer flask placed on an agitating support equipped with a magnetic field. The use of this device provides for a prior step of culturing the sample in a selective culture medium suitable for the growth of the microorganisms being sought; next, these microorganisms are captured by means of magnetic particles onto which are grafted antibodies which bind to the microorganisms being sought. This very specific method for detecting microorganisms solves the problem of the small amount of biological targets in the sample through the culturing step, which makes it possible to multiply the microorganisms being sought and to thus facilitate the detection thereof. While it can be suitable for treating samples having a volume of a few tens of milliliters, its use nevertheless remains limited in terms of volume of the samples, since the problem then arises of obtaining good dispersion of the magnetic capture beads within the sample; finally, such a device is difficult to automate; it does not allow the treatment of several samples in series.
The same limits apply to the device for agitating and separating magnetic beads that is described in patent application US 2005/0013741; this device comprises two permanent magnets placed on either side of a container containing magnetic beads; these magnets are vertically mobile; depending on the movement that they are given, they can either agitate the beads in order to place them or maintain them in suspension, or group them back together in order to separate them from the sample. This device targets containers with a maximum volume of a few tens of milliliters. The problem encountered during the treatment of larger volumes is the difficulty in obtaining good dispersion of the magnetic beads and in subsequently recovering them.
Finally, the Pathatrix device from Matrix Microscience proposes the capture of targets such as pathogenic microorganisms in samples of 250 ml by circulating the sample in a loop in a tubular circuit in which functionalized magnetic capture beads are immobilized on a flat magnet. Since the beads are immobilized, this device produces a low capture yield which does not make it possible in particular to detect targets present at a low concentration.
Thus, it emerges from the aforementioned that no device of the prior art allows sensitive detection of targets present in a small amount in a liquid sample of large volume by means of automated processing.